U.S. Pat. No. 4,616,198 entitled "Contact Arrangement for a Current Limiting Circuit Breaker" describes the early use of a first and second pair of circuit breaker contacts arranged in series to substantially reduce the amount of current let-through upon the occurrence of an overcurrent condition.
When the contact pairs are arranged upon one movable rotary contact arm, such as described within U.S. Pat. No. 4,910,485 entitled "Multiple Circuit Breaker with Double Break Rotary Contact", some means must be provided to insure that the opposing contact pairs exhibit the same contact pressure to reduce contact wear and erosion.
One arrangement for providing uniform contact wear is described within U.S. Pat. No. 4,649,247 entitled "Contact Assembly for Low-voltage Circuit Breakers with a Two-Arm Contact Lever". This arrangement includes an elongated slot formed perpendicular to the contact travel to provide uniform contact closure force on both pairs of contacts.
U.S. Pat. No. 5,030,804 entitled "Contact Arrangement for Electrical Switching Devices" describes providing a pair of cylindrical plates on either side of the rotary contact arms and forming elongated slots within each of the cylindrical plates.
When the rotary contacts are used within a range of differing ampere-rated circuit breakers, the size of the contact arms varies in accordance with the ampere rating such that the accompanying cylindrical plates must be sized accordingly.
It would be economically advantageous to have a wide range of rotary contact circuit breakers having provision for reducing contact wear without having to stock and assemble a wide range of slotted cylindrical plates.
Accordingly, one purpose of the invention is to include means for reducing such contact wear in rotary contact circuit breakers over a wide range of ampere ratings with the smallest number of associated contact assembly components.